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Defense Against Sclerotinia sclerotiorum in Arabidopsis Is Dependent on Jasmonic Acid, Salicylic Acid, and Ethylene Signaling

November 2007 , Volume 20 , Number  11
Pages  1,384 - 1,395

Xiaomei Guo and Henrik U. Stotz

Department of Horticulture, Oregon State University, Corvallis, Oregon 97330, U.S.A.

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Accepted 18 June 2007.

Genotypic differences in susceptibility of Arabidopsis thaliana to Sclerotinia sclerotiorum have not been reported due to the extreme susceptibility of this cruciferous plant. To overcome this limitation, we have established inoculation conditions that enable evaluation of differences in susceptibility to S. sclerotiorum among Arabidopsis mutants and ecotypes. Two coi1 mutant alleles conferred hypersusceptibility to S. sclerotiorum. The plant defensin gene PDF1.2 was no longer induced after challenging the coi1-2 mutant with S. sclerotiorum. Hypersusceptibility of the coi1-2 mutant to S. sclerotiorum was not correlated with oxalate sensitivity. The mutants npr1 and ein2 were also hypersusceptible to S. sclerotiorum. Induction of PDF1.2 and the pathogenesis-related gene PR1 was reduced in ein2 and npr1 mutants, respectively. Actigard, a commercial formulation of the systemic acquired resistance inducer benzothiadiazole, reduced susceptibility to S. sclerotiorum. Based on histochemical analysis of oxalate-deficient and wild-type strains of S. sclerotiorum, oxalate caused a decrease in hydrogen peroxide production but no detectable changes in plant superoxide production or gene expression.

Additional keywords:H2O2, SAR.

© 2007 The American Phytopathological Society